A cylindrical mirror analyzer (CMA) is known as an energy analyzer which is highly sensitive to electrons and ions. The structure of this analyzer is schematically shown in FIG. 6, where an inner cylinder having a radius of R.sub.1 and an outer cylinder having a radius of R.sub.2 are disposed coaxially. The outer cylinder is placed at a negative potential with respect to the inner cylinder. The inner cylinder is provided with slits near its both ends, the slits extending circumferentially. The slits have a width of W. Electrons or ions emerging from a point to be analyzed enter one slit and then pass between the inner and outer cylinders, the point being located close to the axis. Only electrons or ions having energy which are given by a linear function of the potential difference are allowed to pass through the other slit and is then converged onto the axis. Linear convergence occurs independent of the incident angle to the front slit. Where the incident angle is 42.3.degree. and the distance Lo between the analyzed point and the converging point is 5.6038R.sub.2, quadratic convergence take place.
This cylindrical mirror analyzer can analyze only a narrow region. As the analyzed point moves, the output intensity or energy from the analyzer varies sensitively. The region .phi..sub.ok which can be analyzed without producing these problems is less than approximately 1% of the radius R.sub.1 of the inner cylinder of the analyzer. The generally used cylindrical mirror analyzer can analyze only a quite small region having a diameter less than hundreds of microns.
For example, in Auger electron imaging, the surface of a sample is raster-scanned in two dimensions with a primary electron beam to measure the peak intensity P and the background intensity B. The intensity difference (P-B) is calculated. Also, the ratio (P-B)/B is computed. Thus, a two-dimensional image of the sample is displayed. It is customary to make measurements only at two predetermined points E.sub.pk and E.sub.bkg, for saving the time required for the measurements. At the point E.sub.pk, the peak intensity is measured. At the point E.sub.bkg, the background intensity is measured. The prior art technique for presenting a two-dimensional Auger image in this manner is disclosed by N. C. MacDonald and J. R. Waldrop, in Applied Physics Letters, Volume 19, Number 9, November 1971.
However, if the primary electron beam is scanned outside the aforementioned analyzable region .phi..sub.ok, the peak energy shifts considerably. Consequently, it is impossible to determine the peak intensity P and the background intensity B. Especially, where the sample surface is inclined, larger errors occur.